As an example of such article storage facility described above, there is known an article storage facility having an article storage shelf with a purging function described below. This article storage shelf includes a plurality of storage sections for storing a transport container such as an FOUP, etc. accommodating a semiconductor wafer. Each storage section is provided with a feed nozzle as the inactive gas feeding section for feeding inactive gas such as nitrogen gas, argon gas, etc. to the inside of the transport container, in order to prevent contamination of the semiconductor wafer accommodated in the transport container.
Japanese Unexamined Patent Application Publication No. 2010-16199 (Patent Document 1) discloses an example of such article storage facility. With this article storage facility, the flow rate of inactive gas to be discharged from the feed nozzle is varied between a case when a transport container is stored in the storage section and a case when no transport container is stored in the storage section, such that the flow rate of the inactive gas in the case of no transport container being stored in the storage section is rendered smaller than the flow rate in the case of a transport container being stored in the storage section.
The article storage shelf in Patent Document 1 above includes a plurality of storage sections for storing the transport containers and each storage section includes a detecting device for detecting presence/absence of a transport container in this storage section. If the detecting device detects that a transport container is stored in the storage section, the inactive gas is fed to the inside of the transport container by a flow rate (this flow rate will be referred to as the “first flow rate”) sufficient for preventing contamination of the semiconductor wafer accommodated inside this transport container. Conversely, if the detection device detects that no transport container is stored in the storage section, the inactive gas will be discharged from a feed nozzle by a flow rate (this flow rate will be referred to as the “second flow rate”) set smaller than the first flow rate, in order to prevent accumulation of impurity particles in the feed nozzle.
And, the above-described switchover of the flow rate is effected by the flow rate adjusting device. The flow rate adjusting device is configured to set the feed rate of inactive gas to a target flow rate commanded by the controller.
In Patent Document 1, in case a plurality of transport containers were stored at one time in the article storage shelf, the controller will command a target flow rate to each flow rate adjusting device so that the inactive gas may be fed by the first flow rate uniformly to all these stored transport containers. However, if the flow rate required for feeding the inactive gas by the first flow rate to all of the transport containers stored at one time in the article storage shelf exceeds the flow rate of the inactive gas that can be fed from the feed source (e.g. a cylinder of nitrogen gas), the flow rate of inactive gas that can be fed to each transport container will fall short of the first flow rate as the target flow rate. Therefore, even when commanded the first flow rate as the target flow rate, the flow rate adjusting device will be unable to adjust the feed flow rate of inactive gas to this target flow rate, whereby there will occur inconvenience that the inactive gas feeding section can feed the inactive gas only by a flow rate below the target flow rate.
The flow rate adjusting device is sometimes provided with a function of outputting an error if there has developed a situation wherein the condition of the actually fed flow rate falling short of the target flow rate has continued for a set period. In the case of using a flow rate adjusting device having such function as above, as described above, if the condition of the flow rate of inactive gas that can be actually fed to each transport container falling short of the first flow rate as the target flow rate has continued for a set period, an error will issue, so that the normal operation of the facility may become impossible.